The invention concerns a heating unit for heat-transfer fluid for a central heating installation.
In general terms, a central heating installation comprises a pipework circuit in which one or more radiators or convectors are connected, at least one expansion device and at least one heating station able to heat the heat-transfer fluid which is caused to circulate in the circuit.
The heating station of the installation can in particular be a coal, gas or oil boiler, and there also exist electric heating stations.
It would be advantageous to produce a central heating installation in which the heating station consists of one or more electric heating units with a simple and compact structure, and allowing effective and flexible functioning of the installation.
The invention relates to a heating unit for central heating heat-transfer fluid. This heating unit comprises a reservoir having a tubular external wall, a first end wall and a second end wall, these walls delimiting a space which is in substance cylindrical. A first tubular internal partition and a second tubular internal partition, substantially concentric with the tubular external wall, are mounted in the reservoir, the second internal partition having a diameter smaller than that of the first tubular partition. A first annular space is situated between the tubular external wall and the first internal partition; a second annular space is situated between the first internal partition and the second internal partition; a central pipe is situated inside the second internal partition. The second annular space is in communication with the central pipe close to the first end wall and in communication with the first annular space close to the second end wall. The reservoir is provided with an inlet orifice opening out in the first annular space close to the first end wall and an outlet orifice, in the second end wall, opening out in the central pipe. At least one electric immersion heater is mounted in the central pipe, and at least one thermostatic sensor is mounted in the reservoir.
The components making up the heating unit are preferably made from metal.
In particular, the tubular external wall, the first and second end walls and the first internal partition can in particular be made from steel. The second internal partition can also be made from steel. According to another embodiment, this second internal partition is made from copper.
According to a preferred embodiment, the heating unit comprises, in the second annular space, heat transfer elements fixed to the said second external partition.
These heat transfer elements can in particular consist of two rings spaced apart from one another, fixed to the second internal partition and disposed perpendicular to the axis thereof, these two rings having in them several holes and being connected together by means of several metallic bars spaced apart from each other.
So as to have a large surface of contact with the heat-transfer fluid which surrounds them, these metallic bars advantageously have a ribbed external surface. For the same reason, these metallic bars can also carry fins.
The heat transfer elements are produced from a material having good conductivity. The two rings between which the metallic bars are mounted can be made from steel, but are advantageously made from copper. The metallic bars themselves are preferably made from copper.
As already mentioned above, at least one thermostatic sensor is mounted in the reservoir. In order to provide greater safety in functioning, it may be desirable for two thermostatic sensors to be mounted in the reservoir.
According to a particular embodiment, this thermostatic sensor or sensors are mounted in the second annular space.
According to a preferred embodiment, the first annular space is put in communication with the second annular space by means of several openings distributed over the periphery of the first internal partition, close to the second end wall.
The expression xe2x80x9cclose to the second end wallxe2x80x9d means that the distance between the openings and the second end wall is appreciably smaller than (for example, no more than one quarter of) the distance between these openings and the first end wall.
Advantageously, a ring can be mounted in the first annular space, between the tubular external wall and the first internal partition. This ring which, in the axial direction, has in it several holes distributed along its periphery, is situated at an intermediate level between the inlet orifice of the reservoir and the openings which are provided in the first intermediate partition.
The second annular space is advantageously put in communication with the central pipe by the fact that a space is provided between the second internal partition and the first end wall.
According to a particular embodiment, the inlet orifice of the reservoir is provided in the tubular external wall, close to the first end wall. This orifice thus opens out radially in the first annular space.
The reservoir is preferably provided with means enabling it to be fixed to a support.
According to one advantageous embodiment, two electric immersion heaters are mounted in the central pipe of the heating unit.
When the central heating installation in which the heating unit is connected is in operation, only one of these immersion heaters or both immersion heaters may be put in operation, according to circumstances and requirements.
Another aspect of the invention is a central heating installation with a heat-transfer fluid, comprising a pipework circuit in which one or more radiators or convectors are connected, at least one circulation pump, at least one expansion device and at least one heating unit, this installation including at least one room thermostat. At least one heating unit according to the invention is connected in the circuit of this installation, the installation also comprising an automated control station able to receive the signals from the room thermostat or thermostats and from the thermostatic sensors of the heating unit or units, and to control the start-up and stoppage of the functioning of the circulation pump or pumps and of the immersion heater or heaters of the heating unit or units.
The heating installation according to the invention may if necessary comprise two or more heating units according to the invention, these heating units then being connected in parallel in the circuit.
The heat-transfer fluid circulating in the installation is preferably oil and, more particularly, a mineral oil specially designed for heat transfer.
The heating unit or units connected in the circuit are preferably able to heat the heat-transfer fluid to a temperature above 100xc2x0 C.
The installation can in particular be adjusted so that the temperature of the heat-transfer fluid (in particular oil) is limited to a temperature of between 105xc2x0 C. and 110xc2x0 C., at the output from the heating unit or units.